1. Field of the Invention
This invention relates to an apparatus for dissipating heat from a surface and, more specifically, to hybrid pin fin and dimpled heat exchanger device and configurations of designs for this hybrid assembly.
2. Description of Related Art
Heat dissipating devices are used to remove heat and reduce the operating temperature of heat generating components such as a microprocessor or other heat generating systems. The heat dissipating device is typically coupled to the component to transfer heat away by conduction. Heat is then dissipated in the heat dissipating device to a moving fluid such as air, or a liquid such as water or oil. Increasing the overall heat transfer coefficient of the heat dissipating device increases the efficiency of heat removal.
Past innovations to increase the heat transfer coefficient and simultaneously enhancing cooling by extending heat exchanger surfaces in a manner that substantially improves heat dissipation have experienced average to poor results. Increasing the heat transfer means increasing heat transfer surface area and means that either laminar or turbulent fluid flow is utilized. Increasing surface area and turbulent flow by positioning pins perpendicular to the direction of flow is typically used.
Previous art has attempted to increased turbulent flow by creating texture, or by threading circular surfaces of pins. These surface textures have been an attempt to enhance heat exchanging capabilities; however, they have, in fact, actually decreased turbulence near the surfaces as turbulent flow has been converted to less efficient laminar fluid flow.
The same results have occurred when pin heights have been increased, as the effective surfaces of the pin heat exchangers actually decreases exponentially as the length of the pins are extended beyond optimal lengths.
Another compounding efficiency limitation in previous art has been when solutions are attempted with a focus on turbulent flow. Previous art has implemented the use of turbulence, but with a negative result because the resultant turbulence has actually restricted fluid flow through the exchanger, therefore reducing efficiencies.
Recently, there have been attempts at improving the art by using either round or oval pins. All pins were tightly formatted in arrays with textured surfaces, attempting to get greater turbulent exchange. However, the high pin density with sharp edges in close proximity actually substantially reduced fluid flow more dramatically thus not significantly improving heat transfer efficiencies. Similarly, when the spacing of the pins was increased, the turbulence would reduce dramatically and heat exchanger efficiencies would sharply fall off.
Other attempts at improving the art have utilized circular or oval dimples on a flat surface, attempting to strongly increase the heat transfer coefficient. However, the vortex of fluid flow is relatively inefficient and not adequate to provide a viable mechanism for heat transfer in heat dissipation devices.
Furthermore, deeper dimples further retard the desired vortex effect as the increased depth decreases turbulence creating stagnant fluid which ultimately decreases heat transfer. Deep dimples do increase the surface area of exposure to fluid, however, the geometry actually reduces turbulence so that there is actually substantially less efficiency compared to shallow dimples; and thus, this attempt at significant improvement of the heat exchanging art has not been successful.
Applying dimple patterns on flat heat transfer surfaces has not significantly improved heat exchanging efficiency.
All such attempts looking to improve the art of turbulization of fluid flow have been attempted based on a single directional, laminar fluid transmission, which have not resulted in significant improvements in heat transfer efficiency.